Biodegradable polymers have been commercially available for a number of years. Among these polymers, polylactide (PLA) also known as polylactic acid has been used as an environmentally friendly biodegradable alternative to petroleum based polymers such as polyvinyl chloride (PVC), polyethylene terephthalate (PET), high impact polystyrene (HIPS), polyethylene (PE), and polypropylene (PP), in applications such as rigid and flexible packaging, candy wraps, shrink labels, and form-fill seal extrusions. Further, polylactide has been extensively studied in medical implants, suture, and drug delivery systems due to its biodegradability and has been approved for use in various medical devices. Different thermoplastic processes such as extrusion, blow molding, injection molding, and spinning processes are used to make these products. However, the manufacturing cost of thin articles having complex shapes and sizes, such as gloves, condoms, catheters, using PLA has been prohibitably high, or the PLA thin articles were not substantially biodegradable due to non-biodegradable ingredients in PLA formulations.
Polylactic acid polymers can be manufactured from renewable resources, unlike conventional, synthetic petroleum-based polymers, since the lactate from which it is ultimately produced can be derived from fermentation of agricultural by-products such as corn starch or other starch-rich, substances like sugar or wheat. Lactate which is also known as Lactic acid is a natural molecule that is widely employed in foods as a preservative and a flavoring agent. It is the main building block in the chemical synthesis of the polylactide family of polymers. Although it can be synthesized chemically, Lactic acid is procured principally by microbial fermentation of sugars such as glucose or hexose. These sugar feed stocks can be derived from potato skins, corn, wheat, and dairy wastes.
Lactic acid exists essentially in two stereoisomeric forms, which give rise to several morphologically distinct polymers: D-polylactic acid, L-polylactic acid, D,L-polyactic acid, meso-polylactic acids, and any combinations thereof. D-polylactic acid and L-polylactic acid are stereoregular polymers. D,L-polylactic acid is a racemic polymer obtained from a mixture of D- and L-lactic acid, and meso-polylactic acid can be obtained from D,L-lactide. The polymers obtained from the optically active D and L monomers are semicrystalline materials, but the optically inactive D,L-polylactic acid is substantially amorphous.
Degradation of PLA occurs in two stages. First, the ester groups are gradually hydrolyzed by water to form lactic acid and other small molecules, and then these products are decomposed by microorganisms in the environment. In addition, disposal of PLA products is easier than that of traditional polymers, because polylactic acid incinerates cleanly with lower energy yield, thereby permitting a higher incinerator facility throughput. Further, PLA contains no chlorine or aromatic groups, so PLA burns much like paper, cellulose, and/or carbohydrates—generating few combustion by-products.
Disposable gloves are widely used by members of the medical community, the scientific community, and the industrial community to protect the wearer from chemical exposure, mechanical abrasion, environmental hazards, biohazard contamination and to prevent transmission of disease or contaminants. Health care providers frequently wear disposable gloves while performing surgery or other medical or dental procedures such as patient examinations; thus, the gloves are often also referred to as disposable examination gloves or disposable surgical gloves. The disposable gloves are impermeable to biological fluids, tissues and solids produced by the body or other contaminants (human or animal) advantageously protecting the wearer from fomitic (transmission by objects that harbor pathogenic organisms) transmission of pathogens and disease.
Also, disposable gloves are worn by individuals who wish to protect their hands from various chemicals, materials and objects which may irritate, damage or dry out the users skin and which may be harmful or potentially harmful if allowed to contact or permeate the dermal barrier. These gloves may be worn in the occupational setting by scientists, cleaning service workers, food handlers, law enforcement workers, beauticians or other workers having special protection needs. Thus, disposable gloves may also be referred to as protective gloves or industrial gloves. Also some disposable gloves are considered reusable gloves because they can be used multiple times prior to disposal. For example, homemakers may reuse the same pair of household gloves to protect their hands from harsh cleaning solutions or just while washing dishes. Likewise, gardeners or plant service workers may reuse gloves when spraying plants with fungicides or other garden chemicals.
As is known in the art, disposable gloves (and reusable gloves as well as other flexible elastomer articles) are thin and flexible and are manufactured from a variety of polymeric materials herein throughout referred to as “elastomer(s)” or “elastomer material(s)” or “raw material(s)”. These elastomers may be considered a natural rubber as with natural rubber latex (NRL) or a synthetic rubber, or a plastic and include, but are not limited to, a synthetic polyisoprene, a chloroprene (including Neoprene-homopolymer of the conjugated diene chloroprene), a polyurethane (PU), a polyvinyl chloride (PVC), a styrene butadiene styrene (SBS), a styrene isoprene styrene (SIS), a silicone, a butadiene methylmethacrylate, an acrylonitrile, a styrene ethylene butylene styrene (SEBS), an acrylate-based hydrogel, any other elastomer that can be suspended into an emulsion, any other elastomer that is suspendable, soluble or miscible in a solution or plastisol, and combinations thereof.
Regardless of the type of end use application and/or specific thermoplastic used, elastomeric gloves are typically thrown away after a single use, and therefore, a significant amount of waste is generated.
Importantly, many of the polymers utilized in manufacturing disposable gloves are petroleum based and resist environmental degradation. Indeed, the environmental impact of nonbiodegradable plastic waste is a growing concern and alternative disposal methods for such plastics are limited. For example, incineration of synthetic plastics generates toxic emissions and satisfactory landfill sites are becoming increasing limited.
Further, petroleum resources are finite. Indeed, as petroleum reserves decrease in abundance, the raw material and production costs associated with the manufacture of such nonbiodegradable, thermoplastic gloves will increase accordingly. In addition, government regulations may increase disposal and recycling costs for nonbiodegradable plastics to accommodate landfilling and/or environmental impact resulting from use of such materials.
Biodegradable disposable gloves are only very generally known in the art. In particular, PLA is more expensive than many petroleum-derived commodity plastics, and, as such, use of PLA for disposable medical and/or industrial gloves is cost prohibitive—especially given the sheer number of disposable gloves utilized, for instance, in hospitals and clinics. Further, carcinogenicity and toxicity concerns related to the use of certain plasticizers have previously taught against use of PLA polymers in the production of disposable medical gloves.
U.S. Pat. No. 6,393,614 to Eichelbaum discloses a disposable, loose-fitting glove with pockets for carrying an item such as a tampon or sanitary napkin from a patient. While the glove is recited to be biodegradable in theory, no material of construction or degradability specifications are disclosed or suggested. Indeed, the '614 patent does not enable or provide a description of the biodegradable materials or methods of construction/manufacturing considered within the scope of the invention.
U.S. Patent Publication No. 2007/0207282 assigned to the present assignee discloses a polylactic acid glove and method of making the same, the teachings and disclosures of which is hereby incorporated by reference in their entireties to the extent not inconsistent with the present disclosure.
The invention provides improved biodegradable thin articles such as elastomeric gloves and methods of making the same. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.